AC power controller

ABSTRACT

A low voltage AC power controller uses a line coupled capacitor AC to DC converter circuit to obtain energy from AC line power supplied to an AC load and may be used with an external high voltage AC switching device to control power supplied to the AC load. The line coupled capacitor AC to DC converter circuit provides a low power device that senses characteristics of the power supplied to the load and can communicate sensed information and/or receive control information related to the power supplied to the load.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims benefit of provisional application entitled “ACPower Controller”, application No. 61/614,801, filed Mar. 23, 2012,which application is incorporated herein by reference in its entirety.

BACKGROUND

Field of the Invention

The invention relates to electrical devices and more particularly tosensing and control of power supplied to electrical loads.

Description of the Related Art

Growing development across the globe has driven consistent increases inelectric power consumption. The installed base of electrical devices islikely on the order of 1 T. A typical house or business in anindustrialized country has one or more meters, dozens or more circuits(breakers) and hundreds or more loads (devices). On the order of 100billion new electrically powered devices are sold each year, from lightbulbs to motors to appliances. The electrical devices consume theelectrical energy from the electrical power grid supplied in the form ofalternating current (AC) power.

SUMMARY OF EMBODIMENTS OF THE INVENTION

Various embodiments provide a way to actuate (control) and measure(sense) the flow of electric current and voltage associated with ACloads. Various embodiments may utilize a low voltage, CMOS, mixed signalintegrated circuit and an external high voltage AC switching device.

In an embodiment an apparatus includes a line coupled capacitoralternating current (AC) to direct current (DC) converter circuit toobtain power from an alternating current (AC) power line selectivelycoupled to a load. The apparatus further includes a communicationcircuit supplied with power from the capacitor AC to DC convertercircuit to transmit or receive information associated with one or moreaspects related to power supplied to the load.

In another embodiment an apparatus includes an adaptive triac controlcircuit to supply a triac gate drive signal at successively lower levelsof at least one of pulse width and current magnitude to determine aneffective drive signal having a lower level of at least one of pulsewidth and current magnitude than an initial drive signal.

In another embodiment a system includes a plurality of AC power controldevices, each of the devices including a line coupled capacitor AC to DCconverter circuit including a capacitor to obtain power from analternating current (AC) power line selectively coupled to a load; and aradio frequency (RF) communication circuit to send at least onecharacteristic associated with the load to a destination remote from theapparatus through one or more other of the devices connected in acommunication network.

In another embodiment a method includes using a line coupled capacitoralternating current (AC) to direct current (DC) converter circuitcoupled to an AC power line to convert AC power available on an AC powerline to DC power, supplying a communication circuit with the DC power,and transmitting or receiving one or more characteristics associatedwith the power being supplied to the load using the communicationcircuit.

In another embodiment a method includes supplying a triac gate drivesignal at successively lower levels of at least one of pulse width andcurrent magnitude to determine an effective drive signal having a lowerlevel of at least one of pulse width and current magnitude than aninitial drive signal.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention may be better understood, and its numerousobjects, features, and advantages made apparent to those skilled in theart by referencing the accompanying drawings.

FIG. 1 is a block diagram illustrating an embodiment of a powercontroller including features described herein.

FIG. 2 illustrates operation of an actuator of FIG. 1 implemented usinga triac.

FIG. 3A illustrates an embodiment of a line coupled capacitor AC to DCconverter circuit that may be used in the embodiment of FIG. 1.

FIG. 3B illustrates an embodiment of a line coupled capacitor AC to DCconverter circuit that may be used in the embodiment of FIG. 1.

FIG. 4 illustrates a network topology into which a plurality of powercontrollers may be configured.

FIG. 5 illustrates exemplary control of the triac according to anembodiment.

FIG. 6 illustrates leading edge control waveforms associated with atriac.

FIG. 7A illustrates a trailing edge control that may be used forcontrolling power supplied to a load.

FIG. 7B illustrates an exemplary MOSFET circuit that may be utilized toprovide the control illustrated in the waveforms of 7A.

FIG. 8 illustrates an embodiment in which power is supplied through alow impedance gate node of the AC switching device for use by the ACpower controller.

FIG. 9 illustrates a state diagram for an embodiment of a powercontroller.

FIG. 10 illustrates a flow diagram for an adaptive triac gate drivecontroller to adaptively set pulse width according to an embodiment.

FIG. 11 illustrates a flow diagram for an adaptive triac gate drivecontroller to adaptively set current magnitude according to anembodiment.

FIG. 12 illustrates a wiring configuration in which a power controllerdescribed herein may be utilized.

FIG. 13 illustrates another wiring configuration in which a powercontroller described herein may be utilized.

FIG. 14 illustrates another wiring configuration in which a powercontroller described herein may be utilized.

The use of the same reference symbols in different drawings indicatessimilar or identical items.

DETAILED DESCRIPTION

Referring to FIG. 1, illustrated is an exemplary embodiment of a powercontrol device 100 that actuates (controls) and/or measures (senses) theflow of electric current and voltage through an AC load 101. Becausethere are so many electrical devices in a home or business, it isimportant that control and sensing does not significantly add to theelectrical load as that would discourage the use of such monitoring andcontrol devices. Accordingly, one aspect of the power control AC powercontroller 100 is that it manages off-state power to try to simplifyand/or reduce the power requirements for the controller. FIG. 1illustrates major functional blocks that may be associated with one ormore embodiments of the power controller 100 including a line coupledcapacitive AC/DC converter circuit 103 to provide power for otherfunctional blocks of the AC power controller 100, which is describedfurther herein. The AC power controller 100 includes a mixed signalintegrated circuit 105 that has an analog front end (AFE) 107 thatprovides, in an embodiment, among other functionality, measurementcapability related to the power being supplied to the load 101 by powersource 121. For example, the current supplied to the load may be sensedusing well known current measurement techniques such as resistivecurrent sense 109 or magnetic current sense 110. In addition, the AFE107 may include a variable control input 115 and control power beingsupplied to the load 101 based on that input. For example, the variablecontrol input may be a dimmer for a light. In addition a resistor 173may be utilized in some embodiments to provide electrostatic discharge(ESD) protection.

A wide variety of electrical loads may be monitored and/or controlled.For example, the load may be a wall switch/dimmer, an outlet, anelectrical appliance such as a refrigerator, stove, washing machine ordrier, a power strip, AC/DC adapters, light bulbs, light fixtures, ACcircuit breakers (provides circuit level visibility to full house load),an electric meter, wireless connection to thermostats, security,sensors, heating ventilation and air conditioning (HVAC). The examplesshould not be construed to be limiting and any device that utilizes orsupplies electrical current may benefit from use of embodimentsdescribed herein.

In order to control the power supplied to the load 101, the AC powercontroller 100 includes an actuator 111 that controls the power suppliedto the load. In an embodiment, the actuator functions as a switch thatcan be turned on and turned off. The actuator 111 in one embodiment is abidirectional triode thyristor, also referred to as a triac (triodealternating current switch), which can be controlled from the lowvoltage device 105. The triac is a bidirectional switching device thathas two thyristors with a common gate. The triac may operate as shown inFIG. 2 showing leading edge control. Assume an AC wave form 201 shown inFIG. 2. The AC waveform may range from, e.g., 110-240 VAC at 50-60 Hz.The triac turns on to allow current through the triac when a pulse at203 is supplied to the gate of the triac through node 108. The pulse maybe 100 mA at 1.5 V for 100 microseconds. Of course, the pulse width,voltage, and current values utilized can vary according to theparticular triac utilized and/or other system requirements. Thus, thehigh current device (e.g., normal house currents) can be controlled witha low voltage pulse. Once the pulse turns the triac on, the triac stayson until the zero crossing at 207, at which point the triac turns off. A−100 mA magnitude pulse at −1.5 V for 100 microseconds at 205 turns thetriac back on for the negative portion of the AC cycle. One way tocontrol the power supplied to the load is by moving the location of thepulse to vary the duty cycle from 0 to 100% (thereby changing theportion of the waveform that is actually supplied to the load).Actuators such as the triac are typically used when driving resistiveloads such as incandescent bulbs, many LED controllers and someinductive loads.

In an embodiment where the AC power controller uses low power,particularly in the off-state, as described further herein, a linecoupled capacitor alternating current (AC) to direct current (DC)converter circuit is used. An exemplary embodiment of the line coupledcapacitor AC to DC converter circuit includes an on-chip portion 103 (onthe integrated circuit 105), and off-chip capacitors. Additional detailsof the line coupled capacitor AC to DC converter circuit 103 are shownin FIG. 3A. The line coupled capacitor AC to DC converter circuitincludes diodes 301 and 303 and shunt regulators 305 and 307. Thecapacitors in FIG. 3A are also shown in FIG. 1. As can be seen in FIG.1, the capacitors 131, 133 and 135 are off-chip, that is, they areseparate components from integrated circuit 105. Assume the AC powersupply is 120 VAC at 60 Hz. The capacitor 131 charges and dischargesonce every cycle or 60 times a second. Current I₁ charges capacitor 133during the positive portion of the cycle and current I₂ chargescapacitor 135 during the negative portion of the cycle. The diode 301allows current to charge capacitor 133 during the positive portion ofthe cycle (and prevents discharge back into the AC line during thenegative portion of the cycle) and the diode 303 allows current tocharge capacitor 135 during the negative portion of the cycle (andprevents discharge back into the AC line during the positive portion ofthe cycle). The capacitor 131 does not consume power, but transfersenergy to a different phase. The capacitors 133 and 135 store energy foruse by the functional blocks in integrated circuit 105. The totalcurrent obtained is I₁+I₂. The shunt regulators 305 and 307 ensure thatthe capacitors 133 and 135 charge to a predetermined voltage based onthe reference voltages 309 and 311, e.g., 1.8 volts after which anyfurther charge is diverted by the shunt regulators. Note that 1.8 voltsis an exemplary voltage level and other voltage levels may be utilizedaccording to the requirements of particular embodiments. In an exemplaryembodiment the capacitor 131 is a 100 nF capacitor rated at 400 VAC.Capacitors 133 and 135 may be, e.g., 100 μF rated at 3 V. In order towork with 240 VAC power, a peak voltage of approximately 373 volts maybe expected.

FIG. 3B provides another illustration of a capacitor AC to DC converterthat is similar to FIG. 3A with the zener diodes 321 and 323 functioningas the shunt regulators. The average power that can be obtained from theAC supply line may be determined by looking at the average current.Average current is a function of C×V×F, where C is capacitance (e.g.,0.1 μF), V is voltage (e.g., 120 volts), and F is frequency (e.g. 50 or60 Hz). In the embodiment illustrated in FIG. 3B, with efficiency η thepower (P_(IC)) available to the power controller 105 can be determinedas:

i_(x _ rm s) = 2π f_(line )C_(x)(V_(line _ r m s) − V_(x))i_(x _ r m s) ≈ 2π f_(line)C_(x)V_(line _ rm s)$i_{L\;\_\;{ma}\; x} = {\frac{2\sqrt{2}}{\pi}i_{x\;\_\;{rm}\; s}}$P_(IC _ m ax) = V_(z)i_(L _ ma x) P_(IC) = P_(load _ ma x) × ηNote that the size of capacitor 131 can be increased to obtain morepower, but the tradeoff is increased cost. A smaller capacitor may beused if less energy is needed in a particular embodiment.

The DC voltage obtained can be used to power various functional blocksin the AC power controller 100 that constitute the load 105. Forexample, the DC power may be used to power control logic such as themicrocontroller (MCU) 141, communication logic associated with the RFtransceiver 143 or isolation logic 145 to communicate using a suitablecommunication protocol with a device that is isolated from the linevoltage. The reference block 139 provides appropriate voltage (V),current (I), frequency (F), and/or temperature (T) references for use bythe other blocks. Thus, the REF block 139 may include a temperaturesensor to provide sensed temperature, an LC, RC, MEMS, or other one ormore oscillators may be used to provide a desired frequency andappropriate circuits to provide desired voltage and current levels forthe functional blocks. Note that interconnections between the variousblocks in FIG. 1 are not shown for ease of illustration.

The RF receiver/transmitter block 143 provides a wireless communicationsinterface. The use of a wireless interface may provide an embodimentwhich eliminates the need for isolation and thus the need for isolationlogic 145. The RF protocol used by the device may be any appropriateshort-range wireless protocol for transfer of data at relatively lowrates (e.g., <1 mega bits per second (mbps), although other data ratesare also possible). Note that the device may be transmitting and/orreceiving intermittently. However, in other embodiments, where forexample, the device is a repeater node in a mesh network, the device maybe on as much as 100% of the time. An appropriate RF protocol for RFcommunications may be a standards-based protocol based on, e.g., IEEE802.15.4, such as Zigbee or IPv6 over Low Power Wireless Personal AreaNetworks (6LoPAN), or other protocol. The transceiver may transmit andreceive, e.g., at frequencies of 900 MHz, 2.4 or 5 GHz or otheravailable frequencies. There may be multiple power controller devices ina particular location such as a house. As shown in FIG. 4, multiplepower controllers 100 a, 100 b, . . . , 100 n may be coupled andimplemented as part of a mesh network, a point-to-point network, a starnetwork, or in another suitable network topology. For example, powercontroller 100 a may communicate with controller 400 through any or allof nodes 100 b . . . 100 n. Controller 400 may be a household controllerthat provides control functionality for alarm systems, HVAC systems,lighting, communication and entertainment systems, and other electricaldevices. Controller 400 may have wired and/or wireless access throughnetwork 401 to provide remote Internet access to the power controllers.For wireless applications, a simple button on power controller 100 maybe used for association to the network.

Referring again to FIG. 1, one aspect of the RF transceiver in powercontroller 100 is the need for an antenna for RF communication. In anembodiment, an antenna 153 may be implemented as a trace on a printedcircuit board. In addition, or in place of the antenna 153, thetransceiver 143 can couple to the AC lines through capacitor 155 and usethe AC lines as an antenna.

In addition to, or in place of the wireless communication block 143, theAC power controller 100 may include isolation logic 145 to communicatewith a device while ensuring the device is isolated from the linevoltage. The isolation logic may provide capacitive isolation or someother appropriate isolation technique to isolate the AC power controller100 from the destination with which it is communicating. Thecommunications may utilize, e.g., a serial communication protocol inwhich commands may be received and status reported. Communicationsprotocols such as I²C, Serial Peripheral Interface (SPI), or a generalpurpose input/output (GPIO) terminal, or other appropriate communicationinterface may be used with isolation logic 145. Alternatively, or inaddition, such communication protocols may be utilized without isolationto communicate with an external controller through general purposeinput/output (GPIO) block 166. The GPIO block may provide a switch input182 that controls the load (e.g., turns it on and off). Thecommunication interfaces may be used to receive commands, configurationdata, or other control inputs and to report information such as statusbased on sensed information as described further below.

The AC power controller 100 may utilize a low data rate over the RFand/or isolation interfaces to provide control functions such as turningon the load, turning off the load, dimming or brightening the load(where the load provides light). Further, the information related topower supplied to the load based on sensing information can also beprovided using a low data rate. Exemplary information related to thepower supplied to the load may include temperature sense, line voltagesense (resistor or capacitor), or line current sense (resistor ormagnetic). The AC power controller 100 may detect a load change such asa bulb burnout and provide an indication over the appropriatecommunications interface (e.g., wireless, isolated, or non-isolated).The AC power controller 100 may provide line sampling for a programmablenumber of N cycles (N being an integer) of current and/or voltage, storethe results, and transmit the results once the N cycles are complete.The sampling may be run periodically or on a one-time basis according toprogrammable settings. A fast Fourier transform (FFT) may be taken ofthese samples to indicate the harmonic content of e.g., the loadcurrent. The AC power controller may provide power factor measurementand calculation, energy consumption measurements (per hour, per day, orother specified time period), zero cross detection and line frequencysynchronization, overload detection and shutdown (temp, current), and/orload sensing—type (incandescent, fluorescent, motor). Thus, a widevariety of information related to the power supplied to the load may bedetermined by the AC power controller.

The microcontroller unit (MCU) 141 may be programmed to perform theappropriate calculations to generate the aforementioned characteristicsof the power supplied to the load based on the sensed information basedon inputs from sensors in the analog front end 107 or other inputs. Themicrocontroller may utilize the non-volatile memory (NVM) 142 to storenecessary program instructions for the microcontroller to effectuate thesensing and calculations for the information described above. Note thatas the techniques to provide the various sensed information describedherein are well understood by those of skill in the art, they will notbe further described herein. The NVM 142 or other storage may be used tostore the sensed information for later transmission. The sensing andreporting options described above are exemplary and any particularembodiment may sense and report any combination of these or otherinformation related to the power supplied to the load that may be sensedand/or calculated based on sensed information. Alternatively, someembodiments may be configured to act solely as an actuator or solely asan AC power sensing and reporting device.

In order to function satisfactorily as a general actuator, the powercontroller 100 should be sufficiently responsive when a command (orother appropriate control input) is received. For example, the load maybe a light coupled to be powered through the actuator 111. The RFtransceiver 143 may be used to receive wireless commands to dim thelight. Alternatively, variable control input 115 may provide the controlindication to alter the power supplied to the load. There may be atradeoff between fast response time and low power consumption. In orderto maintain low power consumption for the AC power controller, a lowduty cycle (ratio of on time to the measurement period) may be utilizedof e.g., 1/10, 1/100 or 1/1000. For a 1/1000 duty cycle, the device ison for a millisecond every second. In order to satisfy human perceptionsand thus be sufficiently responsive, a satisfactory response time shouldbe provided. Thus, e.g., the device may wake up 10 times a second to seeif a dimmer control has been changed as a result of a change through ahuman interface control (e.g., a dimmer switch) and be on for 1 ms. Thedimmer information may come, e.g., through the variable control 115 or acommand through the RF interface 143, or isolation interface 145. For anRF application, the duty cycle may be significantly higher depending onthe protocol.

FIG. 5 illustrates additional details for controlling the actuator whenthe actuator is implemented using a triac. A positive going pulse 501may be supplied by turning on transistor 503 for e.g., 100 μs to providea 100 mA, 1.5 V pulse to triac 111 to latch the triac (in a conductingstate) for the positive going pulse. A negative going 100 mA, −1.5 Vpulse 505 may be supplied to triac 111 by turning on transistor 507 for100 μs. The capacitors 133 and 135 of FIG. 1 store harvested energy thatare used to supply power for the triac control. The control circuit 504to supply the appropriate control signals for the transistors 503 and505 may utilize, at least in part, microcontroller 141 and/or otherlogic powered by the power obtained by the AC to DC converter.

Referring to FIG. 6, the input voltage to the triac is shown at 601. Theoutput voltage, assumed to be dimmed at approximately 50% is shown at603. In operation in leading edge control, the triac turns off at thezero crossings 606. The control circuit 504 operates to turn on thetriac for the positive portion of the cycle at 605. The control circuit504 operates to turn on the triac for the negative portion of the cycleat 607 to achieve the waveform shown at 603.

While FIG. 6 illustrates leading edge control, trailing edge control isalso widely used as shown in FIG. 7A and is typically implemented withtwo-series connected MOSFETS as shown in FIG. 7B, or a single MOSFETwith steering diodes. The drive conditions are quite different for thesetrailing edge controlled actuators, which are used to drive capacitiveloads such as CFL ballasts, electronic transformers, and some LEDcontrollers. For the trailing edge control, the actuator turns on at thezero crossing as shown at 721. The trailing edge controller 723 may beimplemented, using at least in part, microcontroller 141 and/or otherlogic powered by the DC power obtained from the line. Control logiccauses MOSFET 711 to turn on at rising zero crossings 721 and MOSFET 719to turn on at falling zero crossings 722. As shown in FIG. 7A at 703,when the load is dimmed, the control logic causes the MOSFET 711 to turnoff at 725 and the MOSFET 719 to turn off at 735. In that way, power maybe supplied to the load for only a portion of each cycle.

While the line coupled capacitor AC to DC converter can be used to powerthe device while the actuator is off, when the actuator is on,additional power may be available through the triac gate. For example,referring to FIG. 8, while the triac 111 is latched (in the on state),the gate node 108 provides a low impedance path for power and/or chargefor use by components in the power controller 100. For example, whilethe triac 111 is latched, switches 801 and 803 may be closed to chargecapacitor 802. Switches 807 may be closed (with switch 801 opened and803 closed) to discharge capacitor 802 to provide the stored charge tothe functional blocks 806 or charge pump 811. When the polarity of thetriac voltage is reversed, switches 801 and 803 are closed to charge thecapacitor 802 and switches 809 and 805 are closed (with the otherswitches open) to discharge the capacitor to provide the stored chargeto the functional blocks 806 or charge pump 811. The power available tothe functional blocks through the triac gate node may be higher than thepower available from the line coupled capacitor AC to DC convertercircuit using capacitor 131. The switches 801, 803, 805, 807 and 809 maybe located on integrated circuit 105, while the capacitor 802 may belocated off-chip. The gate current i_(g) _(_) _(max) is determined byv_(g) modulation. V_(g) has a diode temperature (T) coefficient (low athigh T). The average gate current i_(g) _(_) _(avg) is determined by theminimum conduction angle. Thus, for embodiments where dimming isutilized, the available power may be less than if no dimming were used.Power may be obtained using triac gate current in place of, or inconjunction with, the power available through the line coupled AC to DCconverter circuit.

Note that certain circuits of AC power controller 100 may require adifferent voltage level than other circuits. Therefore, the voltage maybe increased, e.g., through the use of a charge pump circuit 811, to anappropriate voltage level for use by certain of the circuits. Forexample, an LED 180 (see FIG. 1) may be utilized on the AC powercontroller 100 to indicate the load is powered or the AC powercontroller 100 is active and have a higher voltage requirement thanother circuits. That LED may be pulsed to save power and may only beactivated when additional power is available through the triac. Certaincircuits present in the analog front end 107 for sensing may only needto be powered when the triac is on and thus may receive their powerthrough the triac gate node. For example, if the triac is off, there maybe no need to sense current.

While one actuator may include a triac as described above, in otherembodiments, a relay, MOSFETS, or other switch capable of switching onand off power supplied to loads may be utilized. FIG. 1 shows a numberof functional blocks that may be combined in various embodiments. Forexample, the AC power controller 100 may operate simply as an AC powercontroller. In another embodiment, the AC power controller 100 may be anAC power controller with an isolated control port. Such a device may beimplemented as a multi-chip module with an isolator die present in themodule. In another embodiment, the AC power controller 100 may be an ACpower controller with wireless transceiver (single chip or multi-chipmodule with a transceiver). The AC power controller may be configured tosense and report various aspects of the power supplied to the load.Various other combinations of functionality and features described abovemay be present in any particular embodiment.

Referring to FIG. 9, in an embodiment the power controller 100 (seeFIG. 1) operates in both a low power mode and a high power mode. FIG. 9illustrates an exemplary power controller state diagram. In 901, thepower controller powers up in state 901. Assuming power is good (PGOOD1)the controller enters the off state 903. In the off state 903 the powercontroller creates a low-power DC supply voltage directly from the ACline using the line coupled capacitor AC to DC converter circuit asdescribed e.g., with relation to FIGS. 3A and 3B. The power controllerlistens on the short range wireless connection (or other communicationinterface) for a command to turn on. The microcontroller (MCU 141) maybe kept in a suspend state keeping its settings from a previouson-state. Miscellaneous analog functions such as providing timing, andappropriate voltage references also need to be performed. Thosefunctions can be accomplished using the DC supply voltage generateddirectly from the AC line using the line coupled capacitor AC to DCconverter circuit. A very low duty cycle to check for a turn-on commandcan help reduce power requirements in this state.

When a command is received on the communications interface to turn-on ora command is received over a human interface (HI) such as a switch, thepower controller enters a low-power on state 905. In the low-power onstate 905, the power controller creates the low-power DC supply voltagedirectly from the AC line using the line coupled capacitor AC to DCconverter circuit. In addition, a secondary AC/DC power converter ispowered-up as described further herein. The time to power up thesecondary AD/DC power converter determines how long the power controllerstays in the low-power on state. The MCU 141 is turned on and theactuator is turned on for a predetermined number of cycles at theappropriate power level corresponding to what was received in theturn-on command. Thus, in the low-power on state 905, the actuator(e.g., triac or MOSFETS) are turned on and the load receives power. Inaddition, an acknowledgement may be sent of the load turn-on and thecommunications interface has to listen for a next command (turn-off,dim, etc.). Note that certain functions such as the acknowledgment orlistening for the next command may be delayed until the full power mode.

Once power from the secondary AC/DC power converter circuit is confirmedgood (PGOOD2), the controller enters the high-power on state 907. In thehigh-power on state a higher power DC supply, e.g., >100 mW, is createddirectly from the AC line utilizing the secondary AC/DC power convertercircuit. The triac is actuated at the required conduction angleconsistent with the received command. The communication circuit listensfor a command to turn-off or otherwise change the load state (e.g., adim or brighten command). The MCU is in an active state and measurementsare taken off line voltage and current as desired. The measured valuesmay be stored for later transmission. If a command is received to turnoff through the communications interface (e.g., short range wireless) orhuman interface, the state machine returns to the off-state 903. In thehigh-power on state, if the power good signal (PGOOD1B) indicates aproblem with power, the state machine returns to the power-up state 901.In the high-power on state 907, if the power good signal indicates aproblem with secondary power (PGOOD2B), the state machine returns to thelow-power on state 905. In the low-power on state 905 or the off state903, if the power good signal (PGOOD1B) indicates a problem with lowvoltage power, the state machine returns to the power-up state 901.

Referring to FIG. 1, the secondary AC to DC converter circuit 160 isshown. The secondary power supply provides more power than the linecoupled capacitor AC to DC converter. In an exemplary embodiment thesecondary power supply 160 supplies approximately 100-300 mW of power.The amount of power depends on the needs of the power controller 100 inthe high-power on state. The control for the AC to DC converter may beprovided by the control functionality on integrated circuit 105. Thesecondary power supply may be implemented as, e.g., a buck converter.Other AC to DC topologies may also be utilized. In addition, the AC toDC converter circuit may be configured as shown as AC to DC convertercircuit 162 (instead of 160) with a connection to NEUTRAL as shown.

In order to guarantee triac gate drive requirements are met, oneapproach is to supply a drive signal of, e.g., 100 mA for 50-100 μs.Another approach that is more energy efficient is to make use of anadaptive gate drive controller. Referring to FIG. 10, an adaptive gatedrive controller, e.g., controller circuit 504 in FIG. 5, selects aninitial I_(G) and t_(on) in 1001, where I_(G) is the gate currentmagnitude and t_(on) is the pulse width. The adaptive gate drivecontroller may be implemented using a programmed microcontroller 141,other logic, or a combination to implement the functionality described,e.g., in FIGS. 10 and 11. Initial values for pulse width and currentmagnitude, along with other control values such as decrement values forpulse width and/or current magnitude, minimum values for pulse widthand/or current magnitude, maximum number of cycles to utilize todetermine an effective gate drive signal, and program code may be storedin non-volatile memory, e.g., NVM 142 in the integrated circuit 105 (seeFIG. 1).

In 1001, in an exemplary embodiment the controller selects I_(G) to be100 mA and t_(on) to be 100 μs. The gate is driven at 1003 with a drivesignal having the current magnitude and pulse width selected. In anembodiment, the triac terminal MT1 is monitored in 1005 by the currentsensor provided by the power controller 100 to ensure the triacswitches. Alternatively, the voltage supplied to the load may bemonitored by the voltage sensor provided by the power controller 100. Atthe next turn-on edge the controller drives the triac gate for a reducedt_(on) time in 1007. For example, the pulse width may be reduced by 10μs or the pulse width may be divided by 2. In 1009, the controllerchecks if drive signal caused the triac to switch. If the triac fails toswitch at that pulse width, the pulse width is increased in 1011. If thetriac switched successfully, the adaptive controller checks if apredetermined number of cycles has been completed or a threshold lowerlimit threshold has been reached, e.g., a pulse width of 10 μs. If thelower limit or threshold has not been reached, the adaptive gate drivecontroller returns to 1007 to continue to reduce t_(on) until a switchfailure, a threshold number of cycles, or a minimum pulse width has beenreached. Once a pulse has been determined acceptable through a YES at1010 or through 1011, the triac is turned on for a predetermined numberof cycles in 1015, e.g., 100 cycles, to ensure that the selected pulsewidth works. If the pulse width works for 100 out of 100 cycles, thenthe drive signal parameters are considered good and are used to drivethe triac. If there is a failure, then the pulse width may be increasedat 1017 and the drive signal is again tested for the predeterminednumber of cycles. Once the drive signal is determined to be good (YES in1016), the temperature may be recorded in 1019 using a temperaturesensor on integrated circuit 105. The pulse width t_(on) is adjusted fortemperature since the temperature coefficient can be significant.

While pulse width can be adaptively determined to reduce the pulse widthof the triac drive signal, in addition or instead of reducing the pulsewidth, the current magnitude can also be reduced. Referring to FIG. 11,an adaptive gate drive controller, e.g., controller circuit 504 in FIG.5 selects an initial I_(G) and t_(on) in 1101, where I_(G) is the gatecurrent magnitude and t_(on) is the pulse width. Such values may bestored in non-volatile memory in the integrated circuit 105. Theadaptive gate drive controller may be implemented using microcontroller141, other logic, or a combination to implement the functionalitydescribed, e.g., in FIGS. 10 and 11.

In 1101, in an exemplary embodiment the controller selects I_(G) to be100 mA and t_(on) to be 100 μs. The gate is driven at 1103 with a drivesignal having the current magnitude and pulse width selected. In anembodiment, the triac terminal MT1 is monitored in 1105 by the currentsensor provided by the power controller 100 to ensure the triacswitches. Alternatively, the voltage supplied to the load may bemonitored by the voltage sensor provided by the power controller 100. Atthe next turn-on edge the controller drives the triac gate with areduced I_(G) in 1107. For example, the pulse width may be reduced by 10mA or by some other factor. In 1109, the controller checks if the drivesignal caused the triac to switch. If the triac fails to switch at thatcurrent magnitude, the current magnitude is increased in 1111. If thetriac switched successfully, the adaptive controller checks if apredetermined number of cycles has been completed or a threshold lowerlimit threshold has been reached, e.g., an I_(G)=10 mA. If the lowerlimit or threshold has not been reached, the adaptive gate drivecontroller returns to 1107 to continue to reduce I_(G) until a switchfailure, a threshold number of cycles, or a minimum current magnitudehas been reached. Once a pulse has been determined acceptable through aYES at 1110 or through 1111, the triac is turned on for a predeterminednumber of cycles in 1115, e.g., 100 cycles, to ensure that the selectedcurrent magnitude works consistently. If the drive signal works for 100out of 100 cycles, then the drive signal parameters are considered goodand are used to drive the triac. If there is a failure, then the currentmay be increased at 1117 and the drive signal is again tested for thepredetermined number of cycles. Once the drive signal is determined tobe good (YES in 1116), the temperature may be recorded in 1019 using atemperature sensor on integrated circuit 105. The pulse width I_(G) isadjusted for temperature in 1121 since the temperature coefficient canbe significant.

While current and pulse width determinations are shown as being doneseparately, they can be done at the same time or sequentially. Thus,both pulse width and current magnitude can be lowered until thresholdsare reached or switching failure occurs. If a failure occurs, one orboth of current magnitude and pulse width can be adjusted upward untilswitching success is achieved. Sequential determinations can also bedone. For example, an appropriate pulse width may be determined first asin FIG. 10 and that pulse width is used as the pulse width to determinean appropriate current magnitude. Alternatively, current magnitude maybe determined first and then pulse width determined through the adaptivegate drive control. The adaptive gate drive control may be performed inresponse to a turn-on command or at another appropriate calibrationtime. Use of the adaptive gate drive mechanism allows less power to beconsumed when controlling the triac.

The power controller described herein may be used in multiple wiringconfigurations. Referring to FIG. 12, illustrated is a common lightswitch wiring configuration, where the load 1201 may be a light. Thepower controller 100 may be disposed in the switch box 1202. A minimumconduction angle may be used to ensure a minimum voltage drop across theAC/DC. The current sense at 1205 is provided on the high side of theload 1203. Note that the AC/DC converter works over a wide input range,e.g., from 30 VAC to full line voltage due to the fact that the triacmay operate only part of the cycle. Note also that if the load goes opencircuit, the power controller become unusable.

In another configuration, as shown in FIG. 13, the power controller 100is connected to neutral through a connection 1303 and controls a remoteload 1301. The power controller has access to full line voltage and theAC/DC converter can operate over a narrower input range. The currentsense 1305 is high side. In this configuration, if the load goes opencircuit, the power controller still works.

In another configuration shown in FIG. 14, the load 1401 is in the samehousing 1403 as the power controller 100. The power controller hasaccess to full line voltage and the AC/DC converter can operate over anarrower input range. The current sense 1405 is high side. In thisconfiguration, if the load goes open circuit, the power controller stillworks.

The description of the invention set forth herein is illustrative, andis not intended to limit the scope of the invention as set forth in thefollowing claims. Other variations and modifications of the embodimentsdisclosed herein may be made based on the description set forth herein,without departing from the scope of the invention as set forth in thefollowing claims.

What is claimed is:
 1. An apparatus including at least one alternatingcurrent (AC) power controller, the AC power controller comprising: aline coupled capacitor AC to direct current (DC) converter circuit toobtain power from an alternating current (AC) power line selectivelycoupled to a load; a communication circuit supplied with power from thecapacitor AC to DC converter circuit to transmit or receive informationassociated with one or more aspects related to power supplied to theload; and a secondary AC to DC power supply circuit to supply power foruse by the AC power controller, the secondary AC to DC power supplycircuit supplying more power than the line coupled capacitor AC to DCconverter circuit; wherein the AC power controller utilizes powersupplied by the line coupled capacitor AC to DC converter circuit in afirst power state while the communication circuit waits for a command tosupply power to the load and the AC power controller utilizes powersupplied from the secondary AC to DC power supply circuit in a secondpower state while power is being supplied to the load, the second powerstate utilizing more power than the first power state.
 2. The apparatusas recited in claim 1 wherein the communication circuit includes a radiofrequency (RF) transceiver circuit powered by the line coupled capacitorAC to DC converter circuit.
 3. The apparatus as recited in claim 1further comprising: a plurality of additional AC power controllers andwherein the additional AC power controllers and the AC power controllerare coupled as nodes in a communication network, each of the additionalAC power controllers including, a line coupled capacitor AC to DCconverter circuit including a capacitor to obtain power from analternating current (AC) power node selectively coupled to a load andsupply DC power for one of the additional AC power controllers; and aradio frequency (RF) communication circuit to send at least onecharacteristic associated with the load; wherein the communicationnetwork is configured to allow one of the nodes to send the at least onecharacteristic associated with the load associated with the one of thenodes to a destination remote from the apparatus through one or moreother of the nodes of the communication network.
 4. The apparatus asrecited in claim 1 wherein the AC power controller is responsive to thecommand to supply power to the load, to switch from the first powerstate to a third power state higher than the first power state and causepower to be supplied to the load in the third power state.
 5. Theapparatus as recited in claim 1, wherein the AC power controller isresponsive to the command to supply power to the load, to switch fromthe first power state to a third power state higher than the first powerstate and cause power to be supplied to the load in the third powerstate while the AC power controller is utilizing power supplied from thecapacitor AC to DC converter circuit; and wherein responsive to powerfrom the secondary AC to DC power supply circuit becoming available, theAC power controller switching from the third power state to the secondpower state.
 6. The apparatus, as recited in claim 1, wherein the ACpower controller further comprises: a control circuit powered by thecapacitor AC to DC converter circuit; and an actuating circuit coupledto supply power to the load according to one or more control signalsfrom the control circuit.
 7. The apparatus as recited in claim 6 whereinthe AC power controller further comprises a sensing circuit to determineone or more power characteristics related to power consumed by the load.8. The apparatus as recited in claim 6 wherein the control circuit ofthe AC power controller is configured to control power delivered to theload according to a communication received over the communicationcircuit.
 9. An apparatus comprising: a line coupled capacitoralternating current (AC) to direct current (DC) converter circuit toobtain power from an alternating current (AC) power line selectivelycoupled to a load; a communication circuit supplied with power from thecapacitor AC to DC converter circuit to transmit or receive informationassociated with one or more aspects related to power supplied to theload; and an adaptive triac control circuit to supply during acalibration phase an initial triac gate drive signal that successfullyswitches on a triac coupled to receive the initial triac gate drivesignal as a triac gate drive signal and to supply as the triac gatedrive signal two or more additional triac gate drive signals havingsuccessively lower levels of at least one of pulse width and currentmagnitude than the initial triac gate drive signal to determine aneffective triac gate drive signal that successfully switches on thetriac, the effective triac gate drive signal having a lower level of atleast one of pulse width and current magnitude than the initial triacgate drive signal.
 10. The apparatus as recited in claim 9, wherein theadaptive triac control circuit is configured to monitor if the triaccoupled to receive the triac gate drive signal switches at each of thesuccessively lower levels.
 11. The apparatus as recited in claim 9,wherein the adaptive triac control circuit is configured to stopreducing levels of at least one of pulse width and current magnitudeafter a predetermined number of the successively lower levels areapplied.
 12. The apparatus as recited in claim 9, wherein the adaptivetriac control circuit is configured to stop reducing at least one of thecurrent magnitude or the pulse width responsive to a particular one ofthe two or more additional triac gate drive signals failing to switchthe triac coupled to receive the triac gate drive signal.
 13. Theapparatus as recited in claim 9, wherein after the effective triac gatedrive signal is determined, at least one of the pulse width or currentmagnitude of the effective triac gate drive signal is varied accordingto temperature.
 14. A method comprising: using a line coupled capacitoralternating current (AC) to direct current (DC) converter circuitcoupled to an AC power line to convert AC power available on an AC powerline to DC power; supplying a communication circuit of an AC powercontroller with the DC power from the line coupled capacitor AC to DCconverter circuit in a first power state while listening in thecommunication circuit for a command to supply power to a load controlledby the AC power controller; using power in the AC power controllersupplied from a secondary AC to DC power supply circuit in a secondpower state while power is being supplied to the load, the second powerstate being a higher power state than the first power state, and whereinthe secondary AC to DC power supply circuit provides more power than theline coupled AC to DC converter circuit; and transmitting or receivingone or more characteristics associated with the power being supplied tothe load using the communication circuit while in the second powerstate.
 15. The method as recited in claim 14 further comprising sensingthe one or more characteristics associated with the power being suppliedto the load.
 16. The method as recited in claim 14 further comprising:responsive to the command to supply power to the load, switching fromthe first power state to a third power state higher than the first powerstate and causing power to be supplied to the load in the third powerstate.
 17. The method as recited in claim 14 further comprising:responsive to the command to supply power to the load, switching fromthe first power state to a third power state higher than the first powerstate with power being supplied by the line coupled capacitor AC to DCconverter circuit in the third power state and causing power to besupplied to the load in the third power state; and responsive to powerfrom the secondary AC to DC power supply circuit becoming available, theAC power controller switching from the third power state to the secondpower state.
 18. The method as recited in claim 14 further comprising:supplying a triac gate drive signal at successively lower levels of atleast one of pulse width and current magnitude to determine an effectivetriac gate drive signal having a lower level of at least one of pulsewidth and current magnitude than an initial triac gate drive signal. 19.The method as recited in claim 18, further comprising: stoppingsupplying the successively lower levels after the triac gate drivesignal fails to switch a triac coupled to receive the triac gate drivesignal.
 20. The method as recited in claim 18, wherein after theeffective triac gate drive signal level is determined, varying at leastone of the pulse width or the current magnitude of the effective triacgate drive signal according to temperature.